README.md

What is this repository for?

HIP allows developers to convert CUDA code to portable C++. The same source code can be compiled to run on NVIDIA or AMD GPUs.
Key features include:

HIP is very thin and has little or no performance impact over coding directly in CUDA or hcc "HC" mode.

HIP allows coding in a single-source C++ programming language including features such as templates, C++11 lambdas, classes, namespaces, and more.

HIP allows developers to use the "best" development environment and tools on each target platform.

The "hipify" tool automatically converts source from CUDA to HIP.

Developers can specialize for the platform (CUDA or hcc) to tune for performance or handle tricky cases

New projects can be developed directly in the portable HIP C++ language and can run on either NVIDIA or AMD platforms. Additionally, HIP provides porting tools which make it easy to port existing CUDA codes to the HIP layer, with no loss of performance as compared to the original CUDA application. HIP is not intended to be a drop-in replacement for CUDA, and developers should expect to do some manual coding and performance tuning work to complete the port.

Repository branches:

The HIP repository maintains several branches. The branches that are of importance are:

master branch: This is the stable branch. All stable releases are based on this branch.

developer-preview branch: This is the branch were the new features still under development are visible. While this maybe of interest to many, it should be noted that this branch and the features under development might not be stable.

Release tagging:

HIP releases are typically of two types. The tag naming convention is different for both types of releases to help differentiate them.

release_x.yy.zzzz: These are the stable releases based on the master branch. This type of release is typically made once a month.

preview_x.yy.zzzz: These denote pre-release code and are based on the developer-preview branch. This type of release is typically made once a week.

How do I get set up?

Simple Example

The HIP API includes functions such as hipMalloc, hipMemcpy, and hipFree.
Programmers familiar with CUDA will also be able to quickly learn and start coding with the HIP API.
Compute kernels are launched with the "hipLaunchKernel" macro call. Here is simple example showing a
snippet of HIP API code:

The HIP kernel language defines builtins for determining grid and block coordinates, math functions, short vectors,
atomics, and timer functions. It also specifies additional defines and keywords for function types, address spaces, and
optimization controls. (See the HIP Kernel Language for a full description).
Here's an example of defining a simple 'vector_square' kernel.

HIP Portability and Compiler Technology

HIP C++ code can be compiled with either :

On the NVIDIA CUDA platform, HIP provides header file which translate from the HIP runtime APIs to CUDA runtime APIs. The header file contains mostly inlined
functions and thus has very low overhead - developers coding in HIP should expect the same performance as coding in native CUDA. The code is then
compiled with nvcc, the standard C++ compiler provided with the CUDA SDK. Developers can use any tools supported by the CUDA SDK including the CUDA
profiler and debugger.

On the AMD ROCm platform, HIP provides a header and runtime library built on top of hcc compiler. The HIP runtime implements HIP streams, events, and memory APIs,
and is a object library that is linked with the application. The source code for all headers and the library implementation is available on GitHub.
HIP developers on ROCm can use AMD's CodeXL for debugging and profiling.

Thus HIP source code can be compiled to run on either platform. Platform-specific features can be isolated to a specific platform using conditional compilation. Thus HIP
provides source portability to either platform. HIP provides the hipcc compiler driver which will call the appropriate toolchain depending on the desired platform.

Examples and Getting Started:

A sample and blog that uses hipify to convert a simple app from CUDA to HIP:

More Examples

The GitHub repository HIP-Examples contains a hipified version of the popular Rodinia benchmark suite.
The README with the procedures and tips the team used during this porting effort is here: Rodinia Porting Guide

Tour of the HIP Directories

include:

hip_runtime_api.h : Defines HIP runtime APIs and can be compiled with many standard Linux compilers (hcc, GCC, ICC, CLANG, etc), in either C or C++ mode.

hip_runtime.h : Includes everything in hip_runtime_api.h PLUS hipLaunchKernel and syntax for writing device kernels and device functions. hip_runtime.h can only be compiled with hcc.